Single-surgeon surgery in laparoscopic colonic resection

PURPOSE

Short-term benefits have been demonstrated for laparoscopic-assisted colectomy. However, minimally invasive surgery is still in an evolutionary phase. In demonstrating that robotic devices also are useful in laparoscopic colonic surgery, it is fundamental to prove that a single surgeon can perform almost the entire operation on his own.

METHODS

A single surgeon performed forty-one, laparoscopic-assisted, colorectal resections with the assistance of a robotic device (Automated Endoscopic System for Optimal Positioning, Computer Motion) maneuvering the laparoscope. A surgical assistant was included only for the open part of the operation. Main outcome measures were conversion rate, total operating time, and percentage of assistance by a second surgeon.

RESULTS

There were no intraoperative complications, one case of conversion to open surgery, and three postoperative complications. The total operating time ranged from 126 to 252 minutes. A single surgeon with the assistance of a robotic device was able to perform approximately 70 percent of an ileocecal resection, 70 percent of a right hemicolectomy, 80 percent of a sigmoid resection, and 85 percent of a anterior rectal resection without further help of a surgeon.

CONCLUSIONS

A single surgeon with the assistance of a computerized robotic system can complete at least two-thirds of a laparoscopic-assisted, colorectal resection on his own. The use of a robotic device in laparoscopic-assisted, colonic surgery is safe, efficient, and feasible, and will prove even more so in future. This also will result in a patient-driven demand for high-standard, minimally invasive surgery.

Oxygen radical-dependent expression of CXC chemokines regulate ischemia/reperfusion-induced leukocyte adhesion in the mouse colon

Activation and accumulation of leukocytes constitute a rate-limiting step in ischemia/reperfusion (I/R)-induced tissue injury. The signalling mechanisms, however, that regulate leukocyte rolling and adhesion in the colonic microcirculation are not known. The objective of the study was to define the role of CXC chemokines (MIP-2 and KC) in I/R-induced leukocyte-endothelial cell interactions in the mouse colon. In C57/B16 mice, colonic ischemia was induced by clamping the superior mesenteric artery for 30 min and leukocyte rolling and stationary adhesion were examined in venules after 120 and 240 min of reperfusion. I/R provoked a clear-cut increase in leukocyte rolling and adhesion in colonic venules. Both MIP-2 and KC were upregulated at the gene and protein level in the reperfused colon. Immunoneutralization of MIP-2 and KC by monoclonal antibodies reduced reperfusion-induced firm adhesion of leukocytes by 73% and 75%, respectively. Interestingly, combined inhibition of MIP-2 and KC additionally decreased leukocyte rolling by 79%, but did not further reduce the number of firmly adherent leukocytes. To study the role of oxygen free radicals (OFRs) in the regulation of CXC chemokine expression, additional animals were pretreated with the xanthine-oxidase inhibitor allopurinol. In fact, allopurinol treatment reduced the colonic levels of MIP-2 and KC by 62% and 64%, respectively. This study elucidates important interactions between OFRs and chemokines in the I/R-induced leukocyte response in the mouse colon. Moreover, our data demonstrate that CXC chemokines play a fundamental role in colonic I/R and that functional interference with CXC chemokines may protect against pathological inflammation in the colon.

Ischemic preconditioning: enough evidence to support clinical application in liver surgery and transplantation?

Ischemia-reperfusion injury of the liver causes severe organ dysfunction after both extended liver resections and liver transplantation. In experimental models, ischemic preconditioning has repeatedly been shown to protect the liver from injury after warm and cold ischemia-reperfusion. Herein, we summarize the experimental and clinical evidence considering protection of tissue by ischemic preconditioning and we conclude that it is now time to initiate prospective randomized multicenter trials, in order to confirm the benefit of ischemic preconditioning for the patients undergoing major liver surgery and liver transplantation.

ETA and ETB receptor function in pancreatitis-associated microcirculatory failure, inflammation, and parenchymal injury

The role of endothelin (ET)A and ETB receptor function in experimental pancreatitis is still not fully understood. Using a rat model of sodium taurocholate-induced pancreatitis and intravital microscopy, we therefore studied whether selective inhibition of ETA receptor function or combined ETA and ETB receptor blockade affects the development of pancreatitis-associated microcirculatory failure, inflammation, and parenchymal injury. Pretreatment with 10 mg/kg body wt of a combined ETA/B receptor antagonist, which is thought to mediate a simultaneous inhibition of both receptors, did not attenuate the pancreatitis-induced microcirculatory failure, inflammatory response, and parenchymal tissue injury. In contrast, pretreatment with a low concentration of the combined ETA/B receptor antagonist (4 mg/kg body wt), which predominantly inhibits the ETA receptor, revealed an improvement of some microcirculatory disorders and a significant attenuation of leukocyte recruitment and tissue injury. Furthermore, pretreatment with a selective ETA receptor antagonist (1 microg/kg body wt) almost abolished pancreatitis-associated capillary constriction, restored functional capillary density, and, consequently, improved overall nutritive perfusion. Importantly, the maintenance of an appropriate microcirculation by selective ETA receptor inhibition was accompanied by a significant attenuation of the inflammation-associated leukocytic response and by a marked reduction of parenchymal injury. Thus our study indicates that pancreatitis-associated development of microcirculatory failure, inflammation, and parenchymal injury is caused by ETs coupling onto the ETA receptor, which therefore may represent a promising target for novel strategies in the treatment of pancreatitis.

Noninvasive analysis of conjunctival microcirculation during carotid artery surgery reveals microvascular evidence of collateral compensation and stenosis-dependent adaptation

OBJECTIVE

Hemodynamically relevant internal carotid artery (ICA) stenosis is a major cause of ischemic stroke. Despite its long-term benefit, carotid endarterectomy may also be associated with severe neurologic deficits. Intraoperative and early recognition of ischemia in the region of the ICA may reduce this risk. To date, direct imaging and quantitative analysis of microvascular structures and function in the human ICA region have not been possible. We purposed to visualize and quantify ischemia/reperfusion-induced microcirculatory changes in the terminal vascular bed of the ICA in patients undergoing unilateral ICA endarterectomy.

METHODS

Sequential analysis of the ipsilateral and contralateral conjunctival microcirculation was performed with orthogonal polarized spectral imaging in 33 patients undergoing unilateral ICA endarterectomy because of moderate or severe ICA stenosis (North American Symptomatic Carotid Endarterectomy Trial score, 75% +/- 13%), before clamping the ICA (baseline), during clamping of the external carotid artery and ICA, during reperfusion of the ICA (intraluminal shunt), during the second clamping of the ICA (shunt removal), after declamping (reperfusion) of the external carotid artery and ICA, and 15 to 20 minutes after the second ICA reperfusion.

RESULTS

During ICA clamping for shunt placement, ipsilateral and contralateral conjunctival capillary perfusion was significantly decreased, but it was completely restored after reperfusion with carotid shunting. Reclamping of the ICA for shunt removal caused microvascular dysfunction, which was significantly less pronounced than that observed during the first clamping. The individual degree of ICA stenosis was inversely correlated with the ipsilateral and contralateral decrease in conjunctival functional capillary density during the first ICA clamping.

CONCLUSIONS

These results suggest adaptive mechanisms of capillary perfusion with increasing stenosis and development of collateral compensatory circulation in the vascular region of the human ICA. Conjunctival orthogonal polarized spectral imaging during unilateral ICA reconstruction enables continuous noninvasive analysis of bilateral conjunctival microcirculation in the terminal region of the ICA and enables monitoring for efficient carotid shunt perfusion during and after endarterectomy.

Inhibition of p53 protects liver tissue against endotoxin-induced apoptotic and necrotic cell death

There is increasing evidence that apoptotic and necrotic hepatocyte death following endotoxin-induced liver injury act as signals for leukocyte sequestration in the liver vasculature. p53 has been implicated to promote apoptosis through trans-activation and down-regulation of specific pro- and anti-apoptotic genes. Here, we report that inhibition of p53 decreases apoptotic and necrotic tissue injury as well as inflammatory cell response. Sprague-Dawley rats were injected intraperitoneally with 2.2 mg/kg pifithrin-alpha (PFT), a p53-inactivating agent, or the vehicle DMSO 30 min before intravenous exposure to lipopolysaccharide (LPS). In vehicle-pretreated animals, LPS induced significant apoptosis and necrosis of hepatocytes, which was associated with intrahepatic leukocyte recruitment, microvascular dysfunction, and enzyme release. Inhibition of p53 effectively attenuated (P<0.05) hepatocellular apoptosis and necrosis, but also reduced leukocyte recruitment and microvascular dysfunction. Western blot analysis revealed that PFT lowered the nuclear-to-cytoplasmic p53 ratio and reduced both activation of NF-kappaB and cleavage of procaspase 3 (P<0.05). In parallel, immunohistochemistry of PFT-pretreated, but not vehicle-pretreated, endotoxic animals exhibited nuclear p53 exclusion and reduced NF-kappaB p65 staining. This indicates that p53 mediates, at least in part, LPS-associated apoptosis and contributes to inflammatory endotoxic tissue injury through leukocyte activation and intraorgan sequestration.

Comparison of surgical stress between laparoscopic and open colonic resections

BACKGROUND

The magnitude of surgical trauma after laparoscopic and open colonic resection was evaluated by examining postoperative serum values of interleukin-6 (IL-6), IL-10, C-reactive protein (CRP), and granulocyte elastase (GE) for further evidence of the benefit realized with minimally invasive approaches in colonic surgery.

METHODS

Altogether, 42 patients with Crohn's disease (n = 20) or colon carcinomas/adenomas (n = 22) were matched by age, gender, body mass index (BMI), and Crohn's Disease Activity Index for either a laparoscopic (n = 21) or an open colonic resection (n = 21). In both groups the postoperative serum levels of IL-6, IL-10, C-RP, and granulocyte elastase were determined, as indicators of surgical stress.

RESULTS

Laparoscopic and open colonic resection caused a significant increase in serum IL-6, IL-10, CRP, and granulocyte elastase levels. The comparison between laparoscopic and open colonic resections, however, showed significantly lower serum IL-6, IL-10, CRP, and granulocyte elastase levels after laparoscopic colonic resection, which was most evident for IL-6 and granulocyte elastase.

CONCLUSIONS

Our study demonstrated that IL-6 and granulocyte elastase may be appropriated particularly to monitor surgical stress. By using these parameters, we found a significant reduction in surgical trauma after laparoscopic surgery, was compared with the open procedure. This supports the clinical findings of a clear benefit for patients undergoing laparoscopic colonic surgery.

Small volume hypertonic hydroxyethyl starch reduces acute microvascular dysfunction after closed soft-tissue trauma

A major pathway of closed soft-tissue injury is failure of microvascular perfusion combined with a persistently enhanced inflammatory response. We therefore tested the hypothesis that hypertonic hydroxyethyl starch (HS/HES) effectively restores microcirculation and reduces leukocyte adherence after closed soft-tissue injury. We induced closed soft-tissue injury in the hindlimbs of 14 male isoflurane-anaesthetised rats. Seven traumatised animals received 7.5% sodium chloride-6% HS/HES and seven isovolaemic 0.9% saline (NS). Six non-injured animals did not receive any additional fluid and acted as a control group. The microcirculation of the extensor digitorum longus muscle (EDL) was quantitatively analysed two hours after trauma using intravital microscopy and laser Doppler flowmetry, i.e. erythrocyte flux. Oedema was assessed by the wet-to-dry-weight ratio of the EDL. In NS-treated animals closed soft-tissue injury resulted in massive reduction of functional capillary density (FCD) and a marked increase in microvascular permeability and leukocyte-endothelial cell interaction as compared with the control group. By contrast, HS/HES was effective in restoring the FCD to 94% of values found in the control group. In addition, leukocyte rolling decreased almost to control levels and leukocyte adherence was found to be reduced by approximately 50%. Erythrocyte flux in NS-treated animals decreased to 90 +/- 8% (mean SEM), whereas values in the HS/HES group significantly increased to 137 +/- 3% compared with the baseline flux. Oedema in the HS/HES group (1.06 +/- 0.02) was significantly decreased compared with the NS-group (1.12 +/- 0.01). HS/HES effectively restores nutritive perfusion, decreases leukocyte adherence, improves endothelial integrity and attenuates oedema, thereby restricting tissue damage evolving secondary to closed soft-tissue injury. It appears to be an effective intervention, supporting nutritional blood flow by reducing trauma-induced microvascular dysfunction.

Allopurinol and superoxide dismutase protect against leucocyte-endothelium interactions in a novel model of colonic ischaemia-reperfusion

BACKGROUND

Leucocyte recruitment is a key feature in ischaemia-reperfusion (I/R)-triggered tissue injury. However, the mechanisms underlying leucocyte-endothelium interactions in the large bowel remain elusive because of a previous lack of models to examine the colonic microcirculation. The aim of this study was to develop and validate a novel method for studying reperfusion-induced leucocyte-endothelium interactions in the colon.

METHODS

The superior mesenteric artery was occluded for 30 min in male C57/Bl6 mice and leucocyte responses were analysed in colonic venules after 30-240 min of reperfusion. Analysis of leucocyte rolling and adhesion in colonic venules was made possible by an inverted approach using intravital fluorescence microscopy.

RESULTS

Thirty minutes of ischaemia and 120 min of reperfusion induced the strongest and most reproducible increase in leucocyte rolling and adhesion. This was associated with a significant increase in colonic levels of malondialdehyde (MDA). Administration of allopurinol and superoxide dismutase reduced I/R-induced leucocyte responses in a dose-dependent manner. Pretreatment with allopurinol attenuated the tissue content MDA in the colon by more than 60 per cent.

CONCLUSION

A new method for examining I/R-induced leucocyte responses in the colonic microcirculation is described. Oxygen free radicals play an important role in triggering leucocyte rolling and adhesion in colonic venules.

New model for in vivo quantification of microvascular embolization, thrombus formation, and recanalization in composite flaps

BACKGROUND

Microthrombi are suggested to be involved in the pathogenesis of composite flap failure. Due to the lack of appropriate experimental models, however, the significance of microvascular thrombus formation and microthromboembolization in free flap failure remains poorly understood. The purpose of this study was therefore to develop a rat hindlimb model that allows tissue-confined in vivo analysis of thrombus formation, thromboembolization, and recanalization within the microcirculation of osteomyocutaneous flaps using intravital fluorescence microscopy.

MATERIALS AND METHODS

Thrombus formation was induced photochemically in individual arterioles and venules of muscle, subcutis, and periosteum. To study thromboembolization, autologous arterial thrombi (40 microm) were preformed in vitro and were injected into the femoral artery supplying the osteomyocutaneous flap.

RESULTS

First platelet deposition was found independent from microvascular red blood cell velocity, while the subsequent growth of thrombus correlated inversely with red blood cell flow measured in the respective microvessel. Time required for complete thrombotic arteriolar occlusion exceeded 700 s, whereas thrombus growth in venules was found to be significantly accelerated ( approximately 300 s) without differences between the individual tissues analyzed. The embolization resulted in a complete shutdown of capillary perfusion in muscle, subcutis, skin, and periosteum. During subsequent spontaneous recanalization, capillary perfusion increased in all tissues to approximately half of baseline, however, without further recovery during the 4-h postembolization period.

CONCLUSIONS

The model presented is suitable to quantitatively study the pathophysiology of microvascular thrombus formation, thromboembolization, and recanalization in composite flaps, and may thus be used to evaluate the effectiveness of novel therapeutic strategies to prevent flap failure.

Acceleration of cutaneous wound healing by transient p53 inhibition

The increase of cell proliferation during early wound healing is thought to be regulated by a decrease of apoptosis. In contrast, the reduction of cellularity during final wound maturation may be controlled by an increase of apoptotic cell death. Herein we studied whether p53 is involved in wound healing-associated apoptosis and whether transient inhibition of p53 is effective to improve the early healing process of cutaneous wounds. Using intravital microscopic and immunohistochemical techniques in hairless mice, we demonstrated that in vivo inhibition of p53 by pifithrin-alpha (PFT-alpha; 2.2 mg/kg ip) accelerates early epithelialization and neovascularization of cutaneous wounds by (i) promoting leukocyte recruitment, (ii) increasing cell proliferation, and (iii) reducing apoptotic cell death. We further show that final wound closure with down-regulation of cell proliferation is not inhibited by PFT-alpha treatment, indicating that transient blockade of p53 function does not affect the process of wound maturation. Western blot analysis revealed that PFT-alpha lowered nuclear but not cytoplasmic p53, implying that cytoplasmic retention of p53 mediates the antiapoptotic effects of PFT-alpha. Furthermore, PFT-alpha significantly increased expression of proliferating cell nuclear antigen protein in whole extracts of cutaneous tissue and caused a rise in proliferation of wild-type, but not mutant, p53-expressing keratinocytes. From our study we conclude that transient inhibition of p53 supports the early cell proliferation required for rapid tissue repair and that this may represent an attractive approach in the treatment of delayed wound healing.

Ovariectomy improves neovascularization and microcirculation of freely transplanted ovarian follicles

To investigate the influence of ovariectomy on the physiological process of neovascularization of ovarian follicles, we harvested follicles with a theca interna at 48 h after pregnant mare's serum gonadotropin (PMSG) treatment of Syrian golden hamsters, for subsequent transplantation onto striated muscle tissue of chronically implanted skinfold chambers of non-ovariectomized PMSG-synchronized hamsters and bilaterally ovariectomized hamsters. Non-ovariectomized non-PMSG-treated animals served as controls. During a 2 week period after transplantation, neovascularization of these freely transplanted grafts was quantified in vivo by assessment of the newly developed microvascular follicular network, its microvessel density, the diameter of microvessels and their volumetric blood flow using fluorescence microscopic techniques. At day 3 after transplantation, capillary sprouts could be observed in all groups studied, finally developing a complete glomerulum-like microvascular network within 5-10 days. In ovariectomized animals, however, vascularization of follicular tissue was found to be accelerated and enhanced when compared with the follicles in both groups of non-ovariectomized animals. This was associated with significantly higher capillary blood perfusion, which may in part represent the graft's adaptive response to pro-angiogenic stimuli due to elevated gonadotropin levels, but might in particular be mediated by gonadotropin-induced release of vasoactive substances. Interestingly, small preantral follicles lacking a theca interna failed to vascularize in either of the groups. In conclusion, the study demonstrates that ovariectomy improves neovascularization and microcirculation of freely transplanted ovarian follicles.

Microvascular transfer-related abrogation of capillary flow motion in critically reperfused composite flaps

Capillary flow motion is defined as rhythmic fluctuations of blood flow in the capillaries. Although critical perfusion has been demonstrated to induce capillary flow motion, little is known about the role of capillary flow motion in microvascular free flaps. The aim of this study was to elucidate the tissue-confined incidence and consequence of capillary flow motion in microvascularly transferred composite flaps, using intravital fluorescence microscopy. In Wistar rats, transferred osteomyocutaneous flaps (n = 7), which were exposed to 1 h of ischaemia during the anastomotic procedure followed by 1 h of reperfusion, were subjected to critical perfusion by stepwise reduction of the femoral-artery blood flow to 0.15 ml min(-1), 0.10 ml min(-1) and 0.05 ml min(-1). Pedicled osteomyocutaneous flaps that were not subjected to ischaemia (n=8) served as controls. In pedicled flaps critical perfusion induced capillary flow motion in the muscle, but not in the skin, subcutis and periosteum. In these flaps, the functional capillary density was preserved in all tissues analysed, including the skeletal muscle. Additional sympathetic denervation of the pedicled flaps did not change the incidence or pattern of capillary flow motion. In contrast, after flap transfer capillary flow motion in muscle tissue did not occur during critical perfusion. As a consequence, a shutdown of perfusion of individual capillaries was observed, resulting in a significant reduction (P<0.05) in functional capillary density, not only in the subcutis, skin and periosteum but also in the muscle itself. Thus, our data suggest that the microcirculatory control of pedicled osteomyocutaneous flaps is preserved during critical perfusion by skeletal-muscle capillary flow motion, whereas this protective regulatory mechanism is lost during the initial reperfusion period after flap transfer, probably not because of denervation but because of surgery- and/or ischaemia-reperfusion-associated injury.

In vivo imaging of physiological angiogenesis from immature to preovulatory ovarian follicles

To develop a model for the study of physiological angiogenesis, we transplanted ovarian follicles onto striated muscle tissue and analyzed the process of microvascularization in vivo using repeated fluorescence microscopy. Follicles were mechanically isolated from unstimulated as well as pregnant mare's serum gonadotropin (PMSG)- or PMSG/luteinizing hormone (LH)-stimulated Syrian golden hamster ovaries and were transplanted as free grafts into dorsal skinfold chambers of untreated or synchronized hamsters. Follicles lacking thecal cell layers did not vascularize regardless whether harvested from unstimulated or PMSG-stimulated animals, but underwent granulosa cell apoptosis, as indicated in vivo by nuclear condensation and fragmentation of bisbenzimide-stained follicular tissue. In contrast, all follicles at 48 hours after PMSG treatment with a multilayered thecal shell exhibited initial signs of angiogenesis within 3 days. Vascularization was completed within 7 to 10 days, comprising a dense glomerulum-like microvascular network. Nature and extent of vascularization of follicles harvested at 72 hours after either PMSG or PMSG/LH treatment did not notably differ from each other when transplanted into the respective synchronized animals. However, follicles with PMSG/LH treatment revealed significantly larger microvessel diameters and higher capillary blood perfusion compared to follicles with sole PMSG treatment, probably reflecting the adaptation to the increased functional demand upon the LH surge. Using the unique experimental approach of ovarian follicle transplantation in the dorsal skinfold chamber of Syrian golden hamsters, we could show in vivo the developmental stage-dependent vascularization of follicular grafts with sustained potential to meet their metabolic demand by increased blood perfusion.

Microcirculatory derangements in acute pancreatitis

During the past decade, a considerable number of experimental studies have confirmed the hypothesis that microcirculatory derangements play a pivotal role in the pathogenesis of acute pancreatitis, including the process of conversion from edematous to necrotizing injury. Predominant microcirculatory disorders are nutritive capillary perfusion failure, with the consequence of prolonged focal hypoxia or anoxia, and inflammation-associated microvascular leukocyte recruitment, CD11b- and intercellular adhesion molecule (ICAM)-1-mediated leukocyte-endothelial cell interaction and loss of endothelial integrity, which may result in both edema formation and necrosis. A variety of proinflammatory mediators, such as oxygen radicals, leukotrienes, platelet-activating factor, and interleukins, but also bradykinin and endothelins, seem to be involved in triggering the manifestations of these microcirculatory disorders. In contrast, the anti-inflammatory interleukin-10, as well as nitric oxide, are thought to be capable of protecting from these pancreatitis-associated microvascular injuries. This knowledge may be encouraging for the development of novel therapeutic strategies, aiming at the attenuation of microcirculatory disorders, and, thus, preventing tissue injury in acute pancreatitis.

Heparin and the nonanticoagulant N-acetyl heparin attenuate capillary no-reflow after normothermic ischemia of the lung

BACKGROUND

Ischemia-reperfusion injury of the lung frequently occurs after cardiopulmonary bypass, after pulmonary thromboendarterectomy, and especially after lung transplantation. Heparin is known to be protective in ischemia-reperfusion injury, but the risk for bleeding disorders may restrict its use in a variety of diseased conditions. Therefore, we tested the efficiency of nonanticoagulant N-acetyl (NA) heparin to protect from postischemic reperfusion injury of the lung.

METHODS

Pentobarbital-anesthetized, mechanically ventilated Lewis rats were heparinized (100 IU/kg) before insertion of catheters. Additionally, animals received either heparin (200 IU/kg; n = 7), NA heparin (1.1 mg/kg; n = 7), or saline (control, n = 7) before ischemia. After normothermic ischemia for 50 minutes, the left lung was reperfused for 120 minutes, or until the death of the animal. The nonischemic right lung was excluded after 10 minutes of reperfusion.

RESULTS

Survival rate at 120 minutes of reperfusion was 7 of 7 and 6 of 7 in the heparin and the NA-heparin group, but 0 in 7 in the control group (p < 0.01). At 30 minutes of reperfusion, PaO2, blood flow through the ascending aorta and mean systemic blood pressure were also significantly higher in the heparin and the NA-heparin group when compared with the control group (p < 0.05). Pulmonary vascular resistance was significantly lower in the heparin and the NA-heparin groups, and histologic examination of the lungs from these groups confirmed reperfusion of nutritive alveolar capillaries by the presence of red blood cells. Lack of red blood cells in the alveolar capillaries of lung specimens from the control group indicated failure of capillary reperfusion.

CONCLUSIONS

Heparin and NA heparin exert similar protection against capillary no-reflow after normothermic ischemia of the lung. This implies that the protective effect of heparin is mediated by properties different from its anticoagulant activity. Thus the nonanticoagulant N-acetyl heparin may pose a safe new therapeutic approach in lung ischemia-reperfusion injury without increasing the risk of hemorrhagic complications.

Loss of physiologic hepatic blood flow control ("hepatic arterial buffer response") during CO2-pneumoperitoneum in the rat

We analyzed whether a compensatory increase of hepatic arterial (HA) flow, known as the "hepatic arterial buffer response" (HABR), may serve for maintenance of liver blood supply during laparoscopy-associated portal venous (PV) flow reduction. We assessed HA and PV flow, as well as hepatic tissue oxygenation (PO2) during CO2-pneumoperitoneum in anesthetized and mechanically ventilated Sprague-Dawley rats (n = 7). Control animals (n = 7) without pneumoperitoneum, but tourniquet-induced PV flow reduction served to demonstrate physiologic HABR. Although stepwise tourniquet-induced reduction of PV flow to 20% of baseline values led to a significant (P < 0.05) increase of HA flow from 4.3 +/- 0.7 mL/min to 9.9 +/- 1.7 mL/min, stepwise intraabdominal pressure-induced decrease of PV flow was paralleled by a linear reduction of HA flow from 2.4 +/- 0.3 mL/min to 1.2 +/- 0.5 mL/min at 18 mm Hg intraabdominal pressure. This loss of HABR was sustained during a subsequent 2 h-period of CO2-pneumoperitoneum contrasting the 2 h of maintenance of HABR in controls. Hepatic tissue PO2 decreased during the 2 h-period of pressure- and tourniquet-induced PV flow reduction by 35% to 51%, respectively. On tourniquet release, all variables regained baseline values, whereas evacuation of the pneumoperitoneum allowed all variables except hepatic PO2 to return to baseline, indicating prolonged tissue hypoxia despite restored total liver blood flow in the Laparoscopic group. Concomitantly, increased liver enzyme activities reflected moderate tissue damage after 2 h of pneumoperitoneum. In conclusion, intraabdominal CO2-insufflation-induced hemodynamic alterations may impair tissue oxygenation and enzyme release, indicating the potential risk for hepatic tissue damage after prolonged periods of laparoscopic interventions.

IMPLICATIONS

We investigated the effect of CO2-pneumoperitoneum on liver blood flow, hepatic tissue oxygenation (PO2) and liver enzyme release. CO2-insufflation reduces portal venous flow without a compensatory increase of hepatic arterial flow ("hepatic arterial buffer response"), resulting in reduced hepatic PO2 and increased ratios of serum alanine aminotransferase to serum aspartate aminotransferase.

Effects of hematocrit on cerebral microcirculation and tissue oxygenation during deep hypothermic bypass

BACKGROUND

One rationale for hemodilution during hypothermic cardiopulmonary bypass (CPB) has been improved microcirculation. However, the optimal degree of hemodilution remains unclear. We therefore studied cerebral microcirculation and tissue oxygenation in a new intravital microscopic model at 3 different hematocrit (Hct) values.

METHODS AND RESULTS

Three groups of 5 piglets with a cranial window over the parietal cortex underwent cooling at Hct of 10%, 20%, or 30%, followed by 1-hour deep hypothermic circulatory arrest (DHCA) and rewarming on CPB. For assessment of functional capillary density (FCD), plasma was labeled with fluorescein-isothiocyanate-dextran. Rhodamine-stained leukocytes were observed in postcapillary venules with analysis for adhesion and rolling. NADH, a natural intracellular fluorophore that increases during ischemia, was measured densitometrically during bypass and DHCA. FCD did not significantly differ from baseline during cooling in any group. However, during early reperfusion (5 minutes) after DHCA, the FCD was significantly higher in the Hct 30% group than in the Hct 10% group. Leukocyte adherence decreased in all groups during CPB and was only moderately increased at the end of the experiment. However, severe hemodilution (Hct 10%) was associated with a significantly greater number of rolling leukocytes relative to Hct 30%.

CONCLUSIONS

Higher Hct does not impair cerebral microcirculation and reduces white cell/endothelial activation after deep hypothermic bypass and circulatory arrest. Severe hemodilution (Hct 10%) results in evidence of inadequate cerebral tissue oxygenation during the cooling phase of CPB. This study suggests that Hct of 30% is preferable relative to lower Hct values during hypothermic CPB, particularly if DHCA is used.

Differential effects of ET-1, ET-2, and ET-3 on pancreatic microcirculation, tissue integrity, and inflammation

The differential effects of endothelin-1, -2, and -3 (ET-1, ET-2, and ET-3) on pancreatic microcirculation, pancreatic tissue integrity, and an initial inflammatory response, which are three distinct characteristics of acute necrotizing pancreatitis, were investigated in a dose-dependent manner in rats using in vivo microscopy. Red blood cell (RBC) velocity and functional capillary density (FCD) were estimated after topical superfusion of the pancreas with ET-1, ET-2, and ET-3 (100, 10, 1 pmol), revealing that ET-1 (100, 10, 1 pmol) or high ET-2 (100 pmol) and ET-3 (100 pmol) cause a dose-related deterioration of exocrine nutritive pancreatic blood flow. Analysis of pancreatic exocrine tissue damage employing the Spormann score displayed that the ET-mediated microcirculatory impairment was paralleled by dose-dependent tissue damage, which was significant compared to the control group (topical superfusion with 1 ml, saline solution 0.9%). Estimation of pancreatic postcapillary leukocyte accumulation by histomorphologically counting choracetate esterase (CAE) stained leukocytes in 50 high-power fields per animal demonstrated a significant increase in postcapillary accumulation of white blood cells, after topical administration of ET-1, ET-2, and ET-3 compared to controls. In contrast to ET-caused effects on microcirculation and tissue impairment, quantitative analysis of postcapillary leukocyte accumulation revealed the most pronounced effect after ET-2 administration but not after ET-1 administration. This demonstrates that ET-1, ET-2, and ET-3 are all able to mediate microcirculatory impairment, tissue damage, and inflammation. However, ET-3-induced damaging effects are less pronounced, while ET-1 most severely alters microcirculation and ET-2 preferentially induces leukocyte-dependent inflammation.

Effects of warm Carolina rinse on microvascular reperfusion injury in rat liver transplantation

Recently, it has been demonstrated that the use of both cold Carolina rinse (CR, 4 degrees C) as well as warm Ringer's lactate (RL, 37 degrees C) attenuates microvascular perfusion failure and leukocyte (WBC) accumulation in liver grafts. The aim of this study was to analyse in vivo whether warming of CR can also lead to a reduction in microvascular reperfusion injury in rat liver transplantation. Syngeneic orthotopic liver transplantation, including arterial reconstruction, was performed in male Lewis rats (180-300 g). Livers were stored in University of Wisconsin (UW) solution for 24 h and rinsed with 15 ml CR which was either cold 4 degrees C (n = 7) or warm 37 degrees C (n = 8) prior to reperfusion. Hepatic microcirculation and WBC accumulation were assessed by intravital fluorescence microscopy, and graft function was determined by analysis of bile flow during the 90-min reperfusion period. Warm CR yielded significantly (P < 0.01) improved sinusoidal perfusion when compared with cold CR; however, the extent of WBC adherence in both sinusoids and postsinusoidal venules did not vary between the groups. In addition, bile flow was slightly increased after warm CR. We conclude that after 24 h of cold storage in UW solution, warming of CR may offer additional benefit in the prevention of microcirculatory reperfusion injury without affecting WBC accumulation.